Most of the speakers for currently available mobile phones basically provide an apparatus which incorporates a dynamic speaker unit and an ECM microphone therein, however, it is known that, with such a combination of components, a voice from a speech opposite party is difficult to be heard in a highly noisy environment. With the microphone, incorporating a noise canceling circuit therein has brought about a certain degree of improvement, however, for a voice which is heard from a speech opposite party, there is no measure against a possible difficulty of hearing besides increasing the sound volume of the speaker. However, any currently available mobile phones offer a limitation in taking such a measure, and it is difficult to avoid occurrence of a situation in which hearing is impossible.
It is known that, for talking in a highly noisy environment, a bone conduction microphone and a bone conduction speaker can be effectively used. The bone conduction speaker unit converts a voice signal into a vibration to transmit it to the skull, and the like, and it is compact and lightweight, and is capable of being used even in a noisy environment, whereby, in recent years, it has widespread use in communication equipment, such as a mobile phone.
In the case where a bone conduction microphone and a bone conduction speaker are used with a piece of communication equipment, such as a mobile phone, these devices are used, being incorporated in a housing of the piece of communication equipment, however, this presupposes that there has previously been provided a space for loading these devices in the housing, and in such space these devices are incorporated (refer to Patent Documents 1 to 3). Accordingly, these devices cannot be used with existing general mobile phones or any other pieces of communication equipment for which these devices are not intended to be loaded therein, and thus there has been provided no space for loading them.
In order to allow a bone conduction speaker to be loaded on an existing mobile phone for use therewith, a mobile phone attachment for use by a hearing-impaired person has been proposed (refer to Patent Document 4). It is composed of a microphone which is installed in tight contact with an ear piece of a mobile phone; a bone conduction speaker which is installed so as to be abutted against a part of the head at the time of being used; a main body unit which includes an amplifier and a battery; and a fixing means for mounting said microphone, said bone conduction speaker, and said main body unit to said mobile phone.
Further, said fixing means has a telescoping part in the middle portion, further having an upper hook which forms one end portion of the fixing means, being loaded with said microphone, said bone conduction speaker, and said main body unit, and being bent to be hooked on an end face part of said mobile phone on the antenna installation side thereof, and a lower hook which forms the other end portion of the fixing means, being hooked on an end face part of said mobile phone on the charging terminal installation side thereof, and thus the type of mobile phone with which this attachment can be used is considerably limited, thereby this attachment lacking versatility. In addition, because the attachment is large as a whole, it presents a problem that, if loaded on a mobile phone, the appearance of the mobile phone is impaired.